Small update - the modem with 3G sim card backup arrived via Star Trak Express yesterday, so alround a win.
Telstra also sent the demon email last night, announcing NBN will be with us in a matter of weeks (FTTP) ...so most assuredly the 3.5 weeks of non-connectivity was a result of this fapping with the infrastructure (supposedly "seamless"...pigs a$$ seamless).
Knowing Telstra, the modem they sent as compensation won't work with NBN